Someone please explain counter-steering to me

Message

sapaul · #41 Unread post by **sapaul** » Tue Apr 25, 2006 5:19 am

You have all got totally wrong. Wanna know what makes the bike turn???????

ME ME ME

I make the bike turn

If I am not on the bike it does not turn.

HA HA.

earwig · #42 Unread post by **earwig** » Tue Apr 25, 2006 6:27 am

jflashg03 · Wed Apr 26, 2006 4:44 pm

hasnt been one completly correct explanation as to what countersteer is. if you dont know precisly what gyroscopic physics is, then its really hard to understand countersteer. if you want to learn, a college level physics or astronautics course would do it or ask me and ill add the one millionth post to this topic. but honestly, who the heck cares? as long as it still works right?

#44 Unread post by **Sev** » Wed Apr 26, 2006 4:55 pm

I've taken my share of physics classes, feel free to explain.

Myself002 · Wed Apr 26, 2006 6:00 pm

how is this thread still going... i mean...damn

jflashg03 · Thu Apr 27, 2006 3:59 am

sigh....

Any spinning object is a gyro as is a spinning morotcycle wheel. newton's first law states that objects in motion stay in motion unless accted upon by an outside force. That is called interia. the inertia of a spinning gyro is called a Moment of Inertia, I [units of kilogram*meters^2]. The angular momentum, H [units of kg*m^2/second], equals I dot angular velocity, W. H is a vector. The right-hand-rule shows us where this vector, H, points. Take your right hand and curl your fingers around the spinning axis of your motorbike wheel in the direction of rotation. Your thumb points in the direction of your wheels angular momentum vector, H.
Since H = I dot W (dot is just a vector multiplier. in our case, it is just a multiplication) or in our case H = I * W, H is proportional to W. Therefore, if we increase angular velocity, we increase angular momentum. As H increases, the vector gets longer. any disturbances applied to our spinning wheel therefore become less effective. think of this..
you have an arrow pointing straight out of the left hub on your front wheel. Thats the H vector ( recall right hand rule). a disturbance to this arrow would be like adding another smaller arrow, deltaH, to the tip of H acting perpendicularly to it, say, pointing to the ground. This would create a resultant H vector at some angle greater then 180, acting from the wheel hub to the tip of deltaH. This new resultant would have to be perpendicular to the wheel hub, therefore, the wheel would have to be leaning to the left at the same angle to make this happen.

H <---------------[] < wheel hub
|
V
deltaH________________ground____________

The resultant H is not shown here. Now imagine that youre traveling high way speed. Recall that the higher the angular velocity, the greater the H vector, thus making it longer...

H <--------------------------------------------[] <wheelhub
|
V
deltaH________________ground____________

Now connect the resultant H from hub to the same deltaH tip. The angle has decreased signifigantly, thus decreasing the amount of lean in the wheel. (Unfortunatly, it is too difficult to draw the resultants and their angles on here)This is called gyroscopic stiffness.
This is what causes the bike to stand up on its own at speed(20mph+). this is why shifting your weight will not lean the bike over at speed, because the wheel's gyro stiffness resists small disturbances(and yes, you leaning your behind over the side is a small disturbance no matter how much you weigh). the only way to lean a gyro is to shift the H vector(since the wheel will always stay perpendicular to it). this can be done by applying a torque to the gyro in the correct orientation. this follows the right hand rule once again. Every torque has an angular momentum. say youre applying a torque to a screwdriver which is being held straight up and down. curl your right fingers about the axis of rotation in the direction of the rotation. your thumb points to the angular momentum vector. if we have a spinning gyro, and we apply a torque to it, our H vector will rotate towards the angular momentum of the applied torque, eventually lining up with it and pointing in the same direction if no other input is applied. The greater out applied torque is, the longer its angular momentum vector becomes. This affects the H vector be making it rotate at a quicker rate.

Now use this to figure how we can lean our motorbike wheel over?
lets say we want to lean right. well, our H vector is pointing to the left; in order to lean the bike to the right, we must move our H vector upwards. Since H follows the applied torque ang. mom. vector, we must apply a torque whereas we will get an ang. mom. vector pointing straight up. right hand rule... point your right thumb up. Which way do your fingers curl? to the left. Therefore, you must torque your handlebars to the left in order to create an upwards ang. mom. vector for our wheel's H vector to follow, thus dragging the wheel into a right hand lean.

camthepyro · Thu Apr 27, 2006 9:31 am

Wow, I don't think I understood a word of that.

niterider · Thu Apr 27, 2006 11:27 am

It really doesn't matter if you don't understand it. I bet that you can ride your bike as good or better than some that can understand all the physics that explain counter steering. I enjoy bike riding a lot more than a physics lesson. Have fun counter steering.

#49 Unread post by **ZooTech** » Thu Apr 27, 2006 11:48 am

I think someone counter-steered this thread right into the toilet...

#50 Unread post by **Sev** » Thu Apr 27, 2006 1:28 pm

So Jflasjhg, with all of that said. Why is it WAY tougher for me to turn if my passenger is leaning out of the turn? Or leaning against me?

They have no input to the front tire, according I should be overcoming their effect without an issue, but if my passenger is leaning hard against the turn then I have to fight them as well.

Are they generating gyroscopic force by leaning?